Semi-insulating Cd1-xZnxTe (x = 0.1) with improved structural perfection has been grown using a gradient freeze technique and active control of the Cd partial pressure in the ampoule, both during crystal growth and cool-down of the ingots. The crystal growth was performed in low temperature gradients to minimize thermal stress and achieve material with low dislocation density. Low growth rates were also used to avoid constitutional super-cooling effects. The gradient-freeze technique allowed the growth of large single crystals extending across the entire cross-section of the ingots. The control of the Cd partial pressure allowed the solidification and cool-down of the ingots close to the stoichiometric composition. As a result, the formation and incorporation of large size (>= 1 micrometers diameter) Te inclusions was avoided during crystallization and ingots with high structural perfection were achieved. The improved structural perfection of the material was found to be associated with large spatial variation in the compensation conditions in the ingots and a resulting spatial variation of the bulk electrical resistivity of the material, ranging from 105 (Omega) cm to 1010 (Omega) cm. Samples cut from the high-resistivity sections of the ingots yield detectors exhibiting good spectral performance and an electron mobility-lifetime product of micrometers (tau) e=1.2x10-3 cm2/V.